In my U.S. Pat. No. 3,913,152, issued on Oct. 21, 1975, I disclose a convertible seat-bed unit in which a back is moved from an inclined position downwardly to a position behind the seat, the seat being moved forwardly and the back and the seat then having upper surfaces substantially in a common horizontal plane for use as a bed. As also disclosed, a linkage arrangement is provided for effecting the proper conjoint movement of the seat and the back in a manner such that the top edge portion of the back is moved substantially in a vertical path, which is especially advantageous in camper vehicles or the like in that the supporting frame of the unit can be rigidly secured to the frame of the vehicle.
In my U.S. Pat No. 4,001,901, issued on Jan. 11, 1977, I disclose improvements including the provision of a construction such that operating parts of the mechanism are behind and below the back of the unit, rather than on the outside, and the provision of a pair of units so arranged that when the seats of both units are moved forwardly, the forward edges thereof are brought into a position adjacent each other. In camper-type vehicles, a dinette table may be removably disclosed between the two units.
In my U.S. Pat. No. 4,037,872, issued July 26, 1977, I disclose a linkage arrangement in which operating parts are behind and below the back of the unit, differing from that disclosed in my U.S. Pat. No. 4,001,091 in that a pivotal connection is provided between seat and back support structures and also in that the support of the seat is through swing arms rather than through the use of rollers riding in track as disclosed in U.S. Pat. No. 4,001,901. The construction disclosed in my U.S. Pat. No. 4,037,872 is thereby somewhat simpler and more economical to manufacture than that disclosed in my U.S. Pat. No. 4,001,901. However, it has been found to have one disadvantage in that because of the pivotal connection between the seat and back support structures, it is not possible to secure both of the seat and back cushions to the corresponding support structures and at the same time avoid producing an open space between edges thereof in the bed condition. Because of this, the back cushion in the construction of U.S. Pat. No. 4,037,872 is not secured to the back support structures and is a separate cushion placed by the user in the proper positions for use in both the seat and bed conditions.
There are many prior disclosures by others of linkage arrangements for seat and back support structures but none are believed to be as pertinent as my patents discussed above. The Logan U.S. Pat. No. 3,282,625 issued Nov. 1, 1966 shows a back support supported by two arms or links and a seat support, which is pivotally connected at about its center point to one end of an arm and is also connected through a link to the point of pivotal connection of the back support to one of its supporting arms. This arrangement has disadvantages over the arrangements disclosed in my patents including the fact that the upper end of the back support moves a substantial distance to the rear in moving from the seat condition to the bed condition.